1. Field
Embodiments of this invention relate to the field of plasma chambers, and more specifically, to create an extended lifetime vacuum seal to form a dielectric break in a plasma chamber.
2. Description of Related Art
Inductively coupled plasmas (ICP) are routinely used in a number of different applications including materials processing, production of activated gases, pollutant abatement and many others. In such devices, a coil is placed in close proximity to, around or within a vacuum chamber. When the coil is excited with radio frequency (RF), the electromagnetic fields induced around the coil create and sustain a gas plasma discharge within the vacuum apparatus. The plasma is coupled to the coil either through the air or through a magnetic core. In the latter case, the sources are called transformer coupled plasma (TCP) sources.
The vacuum chamber is often a metal vessel that includes at least one dielectric gap to avoid the creation of a closed current loop through the chamber. To maintain the vacuum integrity of the chamber, the dielectric section must seal against the metal sections of the chamber forming a high vacuum seal. The vacuum seal is made of an elastic dielectric material, such as an elastomer.
To seal properly, the vacuum seal needs to be compressed so its thickness lies within a certain range specified by the manufacturer. At the same time, the vacuum seal needs to be protected from direct exposure to the plasma. Being elastic, the vacuum seal needs a means to prevent its expansion or contraction when the pressures on both sides of the seal are different. Also, to extend the lifetime of the seal, it is convenient to reduce the exposure of the vacuum seal to the reactive species present inside the plasma chamber. Therefore, a mounting scheme allowing the creation of an extended lifetime vacuum seal to form a dielectric break in a plasma chamber is desired.